How to Calculate Your Target Heart Rate Using The Karvonen Formula

Smart Watch Heart Rate
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When it comes to exercise and weight loss, the single most important thing to pay attention to is your intensity.  How hard you work determines how many calories you burn, how quickly you build endurance, and whether you're getting the absolute most out of your exercise time.

One way to do that is by using The Karvonen Formula, a mathematical formula that helps you determine your target heart rate zone.

The formula involves using your maximum heart rate (MHR) minus your age to come up with a target heart rate range (which is a percentage of your MHR). Staying within this range will help you work most effectively during your cardio workouts.
 

What You Should Know About the Karvonen Formula

The Karvonen Formula is one of the most popular calculations used for figuring out heart rate zones, but there are a couple of issues that have come to light in recent years.

First, the old formula used the number 220 as an average maximum heart rate which, research has shown, is just plain wrong. It t doesn't take into account the differences in heart size and heart rates that exist in all of us. In fact, it's been shown to regularly underestimate heart rate zones for 90% of people studied.

In the example below, you'll see the new number scientists have come up with for MHR, 206.9. That still won't fit every person, but it may give results that are closer to reality.

Second, research has found that women have a different heart rate response to exercise so, again, the formula changes for women. In this case, it becomes  206 - (.88 x age) = MHR instead of 206.9

That said, below are a couple of examples using the Karvonen Formula to calculate heart rate zones.

First, we'll take a 23-year-old man with a resting heart rate of 65 beats per minute (*to get your resting heart rate, take your pulse for one full minute when you first wake up in the morning or after you've rested for a while).

This formula also includes an updated calculation of maximum heart rate (the previous formula was 220 - age, which has now been shown to be inaccurate):

The Karvonen Formula for a Man


206.9 - (0.67 x 23 (age)) = 191
191 - 65 (resting heart rate) = 126
126 * 65% (low end of heart rate zone) OR 85% (high end) = 82 OR 107
82 + 65 (resting heart rate) = 147
107 + 65 (rhr) = 172
The target heart rate zone for this person would be 147 to 172

The Karvonen Formula for a Woman

For the next scenario we'll take a 49 year old woman with a resting heart rate (RHR) of 65:

206 - (.88 x 49) = 163163 - 65 (RHR) = 98
98 * 65% (low end of heart rate zone) OR 85% (high end) = 64 (65%) or 83 (85%)
64 + 65 (RHR) = 129
83 + 65 (RHR) = 148
The target heart rate zone for this person would be 129-148 beats per minute.

Of course, if you have a math phobia like I do, you can always use an online calculator such as this Target Heart Rate Calculator.  Keep in mind that this calculation relies on the old 220-age formula, which can be wrong by as much as 12 beats, so you should use the results as a guideline and adjust your heart rate to match your Perceived Exertion.

Monitoring Your Heart Rate

Once you get your heart rate, how do you monitor it?  The easiest way is to use a Heart Rate Monitor. There are tons out there with just about every bell or whistle you could think of, from GPS tracking to monitoring your sleep.

Two great options:

  1. The Apple Watch - You can actually get your heart rate without having to wear a chest strap and the watch tracks your activity throughout the day, allowing you to record workouts, keep track of how many steps you've taken and even reminding you to stand up if you've been sitting too long.  It also lets you control your music on your iPhone, which is a must for outdoor workouts.  You never even have to take out your phone, which is handy.
  2. The FitBit Charge ​- This is another option for tracking your heart rate without a chest strap and it's much cheaper than the Apple Watch.  You can track all the important things, steps, distance, and calories burned along with your heart rate, which makes the calories burned more accurate.  This can also be used to monitor your sleep every night, although the watch itself is a little bulky.

Of course, you don't need a heart rate monitor, but it really does help to see the numbers in black and white. That alone may motivate you to work just a little harder.

Sources:

Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001 Jan;37(1):153-6.

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